Conventional pumping methods consist in setting in a well a pump plunged in the effluent produced by a geologic formation crossed by a drain hole drilled from the well. The single effluent suction point is located substantially in the vicinity of the pump. The pump delivers the effluent towards the surface by means of a tubular pipe connecting the pump to the surface. The pump is either electrically driven, and in this case, a cable lowered into the well with the pump provides the pump motor with electric power, or mechanically driven through pumping rods driven from the surface by a longitudinal reciprocating or rotational motion. The pump may be of the reciprocating piston type or a rotary pump, for example of the "MOINEAU" type.
In case the drain hole crosses the layers producing the effluent over a great length, for example when the drain hole is substantially horizontal in the geologic reservoir, the pressure drops due to the flow over a great length of the drain hole may become quite significant. In this case, the conventional method tends to develop less efficiently the drain hole zones which are at the furthest distance from the suction inlet of the pump. Furthermore, when the drain hole crosses layers exhibiting permeability and/or effluent composition heterogeneities, the fluids of greater mobility will be produced in preference to the others. In the particular case of water inflows in a zone of the drain hole, the other zones located on the opposite side of the pump with respect to the water inflow zone will be developed little efficiently or maybe no longer at all. It is the same when the drain hole geometry provides traps for the lighter fluids.